The present invention relates to an optical illumination device used for illuminating an optical spatial modulation element, for example, and a projection display device capable of projecting an optical image formed on the optical spatial modulation element through a projection lens onto a screen.
Conventionally, as video equipment for a wide screen, projection display devices using various optical spatial modulation elements have been known. For example, these displays have translucent and reflective liquid crystal panels as optical spatial modulation elements, allow a light source to illuminate liquid crystal panels, form optical images on the liquid crystal panels in response to video signals supplied from the outside, and enlarge and project the optical images on screens through projection lenses.
When a projection display device is configured, it is important to achieve large optical output and to provide a bright projected image with high image quality. In order to achieve such a display, it is important to achieve an optical illumination system which can efficiently condense light emitted from a lamp and can evenly illuminate an optical spatial modulation element. Japanese Patent Laid-Open No. 3-111806 and No. 5-346557 disclose an optical illumination device using an optical integrator and a glass rod. Such a device forms a light-emitting surface, which is similar to an optical spatial modulation element in shape, and forms an image of the light-emitting surface on the optical spatial modulation element through a relay lens and so on, thereby achieving high efficiency and highly even illumination.
Meanwhile, regarding an optical illumination system used for a projection display device, for example, in some applications and configurations that include illumination on a reflective optical spatial modulation element and projection with a shifted axis, an illuminating light beam is emitted in a direction having predetermined inclination with respect to the optical spatial modulation element. However, in the case of oblique illumination using the above conventional optical illumination systems, regarding an illuminating light beam formed on an emitted surface, the image-forming condition is maintained near an optical axis but is not maintained at a position away from the optical axis. Hence, it is difficult to efficiently condense light on an effective region on the emitted surface. Further, the problem is that a figure is distorted with respect to the inclining direction of the emitted surface, which results in uneven brightness.
In order to efficiently illuminate a surface inclined with respect to an optical axis, it is necessary to realize an optical illumination system for satisfying an image-forming condition of an inclined object that is referred to as a so-called shine-proof condition. Although the condition rule provides an image-forming condition of two surfaces inclined to each other but does not solve a problem in that a figure is distorted with respect to an inclining direction of an emitted surface and uneven brightness occurs. Such a problem has essentially occurred in oblique illumination.
In response, as a configuration for repeating twice the shine-proof condition, a method for solving the problem of oblique image-formation is disclosed. (e.g., Japanese Patent Laid-Open No. 4-27912).
FIG. 9(a) shows an example of a basic configuration of a conventional projection display device.
The conventional projection display device is constituted by a lamp 121, a concave mirror 122, a condenser 123, a light bulb 124, a first lens 125, an intermediate image-forming surface 126, a reflection mirror 127, a second lens 128, and a screen 129.
Light emitted from the lamp 121 is condensed by the concave mirror 122, and a single beam of light is formed so as to be almost rotationally symmetric with respect to an optical axis.
The condenser 123 illuminates the entire region of the light bulb 124 by using the single beam of light and condenses light passing through the light bulb 124 near an object-side focus 125a of the first lens 125.
For example, a translucent liquid crystal panel is used as the light bulb 124 and forms an optical image in response to a video signal.
The first lens 125 forms the intermediate image-forming surface 126 using light passing through the light bulb 124. At the same time, light condensed through the condenser 123 passes near the focus 125a of the first lens 125, so that the light is emitted from the first lens 125 as substantially parallel light which surrounds the intermediate image-forming surface 126.
The light bulb 124 and the intermediate image-forming surface 126 are inclined to each other with respect to the optical axis 125b of the first lens 125 so as to satisfy the shine-proof condition.
The reflection mirror 127 disposed near the intermediate image-forming surface 126, for example, uses minute reflecting surfaces 127a that are arranged in two dimensions as enlarged in FIG. 9(b), so that the reflection mirror 127 allows light emitted from the first lens 125 to efficiently enter the second lens 128.
The second lens 128 forms an image of the intermediate image-forming surface 126 again on the screen 129. The intermediate image-forming surface 126 and the screen 129 are inclined to each other with respect to the optical axis 128b of the second lens 128 so as to satisfy the shine-proof condition.
According to the above configuration, figure distortion appearing on the first lens 125 can cancel figure distortion appearing on the second lens 126. Thus, on the screen 129, it is possible to form an image conjugated to an optical image on the light bulb 123 without distortion. Moreover, since a beam of light emitted from the first lens 125 is substantially parallel light, there brings an advantage in that it is possible to reduce loss of light in an optical path from the first lens 125 to the second lens 128.
The projection display device of FIG. 9(a) solves figure distortion caused by inclined image formation and brightness gradient caused by the distortion, and efficiently guides light emitted from the lamp to the screen, so that a bright projected image is obtained without distortion. Therefore, when the above configuration is applied to an optical illumination system, it is possible to efficiently illuminate an optical spatial modulation element inclined with respect to an optical axis. However, the following problem arises.
To be specific, when the shine-proof condition is repeated twice regarding oblique image formation, the optical axes of the first lens and the second lens are largely refracted. Hence, a means of bending an optical path is necessary. In FIG. 9(b), a minute reflection mirror array having minute reflection mirrors aligned in two dimensions is disposed near the intermediate image-forming surface so as to form the above means. However, since the intermediate image-forming surface has a conjugating relationship with the screen, images of edges and the like of the minute reflection mirrors are formed on the screen.
Namely, in the conventional optical illumination device or projection display device, a problem (first problem) arises in which images of edges and the like of the minute reflection mirrors of the optical path bending means are formed on the screen.
Secondly, since light converged by the condenser illuminates the light bulb in the configuration of FIG. 9(a), brightness on the light bulb, which is inclined with respect to an optical axis of a light source, has asymmetric distribution with respect to the optical axis. The distribution of brightness on the light bulb is substantially reproduced on the screen by the effect of the above twice image formation, so that an image having brightness distribution asymmetric with respect to the optical axis is formed on the screen.
Namely, in the conventional optical illumination device or projection display device, a problem (second problem) arises in which an image having brightness distribution asymmetric with respect to the optical axis is formed on the screen.
In view of the above-mentioned first problem, the present invention has as its object the provision of an optical illumination device and a projection display device, by which images of edges and the like of minute reflection mirrors of an optical path bending means are not formed on the screen.
Further, in view of the above-mentioned second problem, the present invention has as its object the provision of an optical illumination device and a projection display device, by which an image having brightness distribution asymmetric with respect to an optical axis is not formed on a screen.
To solve the above-described problems, one aspect of the present invention is an optical illumination device of illuminating an illuminated region inclined with respect to an optical axis, comprising:
a light source,
a front optical illumination system of condensing light emitted from said light source,
a light transmitting element inputted with said condensed light beam, for forming a first light-emitting surface; and
a relay optical system for forming a second light-emitting surface on said illuminated region using light passing through said first light-emitting surface, wherein
said relay optical system substantially conjugates said first light-emitting surface and said second light-emitting surface to each other, said light-emitting surfaces being inclined with respect to an optical axis of said relay optical system, and
said light transmitting element corrects a traveling direction of said incident light beams to form said first light-emitting surface such that an outgoing light beam is effectively incident on said relay optical system, and said light transmitting element forms said first light-emitting surface such that said first light-emitting surface has a brightness gradient in a direction in which brightness gradient appearing in said relay optical system is canceled.
Another aspect of the present invention is the optical illumination device according to the 1st invention, wherein said front optical illumination system includes an optical integrator element for allowing said condensed light beam to have substantially even brightness distribution.
Still another aspect of the present invention is the optical illumination device according to the 2nd invention, wherein said optical integrator element is composed of a first lens array and a second lens array.
Yet still another aspect of the present invention is the optical illumination device according to the 1st invention, wherein said illuminating transmitting element is any one of an eccentric lens, a double-convex lens, a graded index lens, a plastic aspherical lens, a Fresnel lens, and a prism element that are made eccentric with respect to an optical axis of said front optical illumination system.
Still yet another aspect of the present invention is the optical illumination device, wherein said eccentric lens has an aspherical surface.
A further aspect of the present invention is the optical illumination device, comprising an irradiation angle correcting element near an entry side of said illuminated region.
A still further aspect of the present invention is an optical illumination device of luminating an illuminated region inclined with respect to an optical axis, comprising:
a light source,
a light-condensing optical system which forms a single light beam by condensing light emitted from said light source to form a first light-emitting surface substantially intersecting said optical axis,
a first relay optical system of forming a second light-emitting surface using light passing through said first light-emitting surface, and
a second relay optical system of forming a third light-emitting surface on said illuminated region using light passing through said second light-emitting surface, wherein
said first relay optical system substantially conjugates said first light-emitting surface and said second light-emitting surface to each other, said light-emitting surfaces being inclined with respect to an optical axis of said first relay optical system,
said second relay optical system substantially conjugates said second light-emitting surface and said third light-emitting surface to each other, said light-emitting surfaces being inclined with respect to an optical axis of said second relay optical system, and
said first relay optical system provides to said first light-emitting surface a brightness gradient in a direction in which brightness gradient appearing on said second relay optical system is canceled, and forms said second light-emitting surface.
A yet further aspect to the present invention is the optical illumination device, comprising optical bending means of bending an optical path near said first light-emitting surface or said second light-emitting surface.
A still yet further aspect of the present invention is the optical illumination device, wherein said optical path bending means is any one of an eccentric lens, a double-convex lens, a graded index lens, a plastic aspherical lens, a Fresnel lens, and a prism element that are made eccentric with respect to an optical axis of a light-condensing optical system for forming said first light-emitting surface or an optical axis of said second relay optical system.
An additional aspect of the present invention is the optical illumination device, wherein said eccentric lens has an aspherical surface.
A still additional aspect of the present invention is the optical illumination device, comprising an irradiation angle correcting element near an entry side of said illuminated region.
A yet additional aspect of the present invention is a projection display device, comprising:
said optical illumination device,
a space modulator of forming an optical image in response to a video signal disposed substantially at the same position as said second light-emitting surface, and
a projection lens of projecting an optical image of said space modulator.
A still yet additional aspect of the present invention is a projection display device, comprising:
said optical illumination device,
a space modulator of forming an optical image in response to a video signal disposed substantially at the same position as said third light-emitting surface, and
a projection lens of projecting an optical image of said space modulator.
A supplementary aspect of the present invention is a projection display device, comprising:
said optical illumination device
a space modulator of forming an optical image in response to a video signal disposed substantially at the same position as said first light-emitting surface, wherein
said first relay lens system and said second relay lens system project an optical image of said space modulator on a screen disposed on said illuminated region.
A still supplementary aspect of the present invention is the projection display device, comprising a rotating color wheel having a color wheel like a disk near said first light-emitting surface to selectively transmit light of red, green, and blue, and
said optical spatial modulation element is subjected to color sequential driving.
A yet supplementary aspect of the present invention is the projection display device, comprising a rotating color wheel having a color wheel like a disk near said second light-emitting surface to selectively transmit light of red, green, and blue, and
said optical spatial modulation element is subjected to color sequential driving.